1. Field of the Invention
The present invention pertains to a method for making a spliceless coated abrasive belt reinforced by a continuous elongate fibrous material, and the product of this method.
2. Related Art
Coated abrasive articles generally contain an abrasive material, typically in the form of abrasive grains, bonded to a backing by means of one or more adhesive layers. Such articles usually take the form of substrates, discs, belts, bands, and the like, which can be adapted to be mounted on pulleys, wheels, or drums. Abrasive articles can be used for sanding, grinding, or polishing various surfaces of, for example, steel and other metals, wood, wood-like laminates, plastic, fiberglass, leather, or ceramics.
The backings used in coated abrasive articles are typically made of paper, polymeric materials, cloth, nonwoven materials, vulcanized fiber, or combinations of these materials. Many of these materials alone provide unacceptable backings for certain applications because they are not of sufficient strength, flexibility, or impact resistance. As a result, early failure and poor functioning can occur, at least in certain applications of these backing materials in a nonreinforced state.
In a typical manufacturing process, a coated abrasive article, including the backing and abrasive coating, among other things, is made in a continuous web form and thereafter converted into a desired construction, such as a substrate, disc, belt, or the like. One of the most useful constructions of a coated abrasive article is an endless coated abrasive belt, i.e., a continuous loop of coated abrasive material. In order to form such an endless belt, the web form is typically cut into an elongate strip of a desired width and length. The ends of the elongate strip of the preformed substrate of coated abrasive article are then joined together to create a "joint" or a "splice".
There are two commons ways to join the free ends of an elongate strip to make a spliced endless belt. These are respectively referred to as a "lap" splice or a "butt" splice. In a "lap" splice, the two free ends of the elongate strip are respectively beveled to have a top end and a bottom end which can be superposed to form a joint without causing a significant change in the overall thickness of the belt. The beveling on what will become the bottom end is typically accomplished by removing abrasive grains and material from the abrasive surface of one end of the strip and removing part of the material from the backing or underside of the other end of the strip to provide what will become the top end of the splice. The beveled ends are then overlapped and joined adhesively or mechanically.
For the "butt" splice, the two free mating ends of the elongate strip are brought into a juxtaposed relationship at a juncture line. The bottom surface of the backing at each end of the elongate strip, such as a preformed substrate of coated abrasive article, typically is then coated with an adhesive, mechanically secured, or otherwise attached, and maybe overlaid with a strong, thin, tear-resistant, splicing media in the joint area.
Lap and butt splices, while providing a satisfactory belt for many applications, may be undesirable for other applications because they typically create a discontinuity in the abrasive coating layer at the outer surface, i.e., the abrasive coating surface, of the splice site. This type of splice is generally exemplified in U.S. Pat. No. 2,391,731 (Miller), U.S. Pat. No. 3,333,372 (Gianatsio) and U.S. Pat. No. 4,736,549 (Toillie). A discontinuity in a coated abrasive can cause an undesirable mark in the surface of a workpiece being finished. These marks are often referred to as "chatter".
Other background art includes:
U.S. Pat. No. 289,879 (Almond) pertains to a polishing tool comprising abrasive grains adhered to a tubular backing.
U.S. Pat. No. 2,032,356 (Ellis) discloses a coated abrasive having a seamless tubular fabric backing.
U.S. Pat. No, 2,404,207 (Ball) pertains to a seamless coated abrasive article having a fibrous nonwoven backing. The fibrous nonwoven backing can be saturated with an adhesive and contain other reinforcing fibers.
U.S. Pat. No. 2,411,724 (Hill) teaches a method for making an endless tubular coated abrasive, wherein a thermoplastic or thermosetting adhesive is extruded to form a backing, in which abrasive grains are embedded while the backing is molten. In another embodiment of that invention, the backing can comprise a liner of reinforcing strands over which is coated the thermoplastic adhesive.
French Patent Application Publication No. 2,396,625 published 2 Feb. 1979 teaches a seamless endless coated abrasive belt that is made by the continuous weaving of a cloth backing. This reference also describes a spliced backing having a sinusoidal splice.
French Patent Publication 2,095,185 published 2 Nov. 1972 (Ponthelet) discloses an abrasive product having a nonwoven backing which may be reinforced with filaments placed in either the transversal direction, longitudinal direction or as a grid form. Where the filaments are arranged only in one direction, the filaments are said to be maintained in a parallel arrangement as held down by a veil made of natural, artificial or synthetic fibers.
PCT Published Patent Application No. WO 93/12911 (Benedict et al.) published 8 Jul. 1993 and owned by the present assignee, pertains to a method of making a spliceless coated abrasive belt having a backing which includes between about 40 to 99% by weight of an organic polymeric binder and an effective amount of a fibrous reinforcing material engulfed within the organic polymeric binder material. This reference described preparing a loop of liquid binder material having fibrous reinforcing material therein around the periphery of a drum, and then solidifying the binder material to form the endless, spliceless belt.
In many abrading applications, it is desired to use an endless coated abrasive belt that has a backing with certain desired physical properties. These properties include relatively low stretch, relatively high tensile strength value and relatively high adhesion between the backing and the abrasive coating. Although Benedict et al. represent a significant advance in the art of making coated abrasive belts, alternate approaches to improve the physical properties of the backing continue to be sought.
PCT Published Patent Application No. WO 95/00294 published 5 Jan. 1995 (Schneider et al.) and owned by the present assignee, pertains to a method of making an endless, spliceless belt. A flowable organic material is spin casted to form an uncured endless loop of organic material. Abrasive particles are then inserted into the spin caster, spun therein until they are engulfed into the organic material which is then solidified to form an endless, spliceless abrasive belt.
U.S. Pat. No. 2,349,365 (Martin et al.) involves a flexible coated abrasive article in which the backing comprises a substrate of plastic material reinforced with a substrate of cloth or paper.
PCT Published Patent Application No. WO 86/02306 publication published 24 Apr. 1986 (Hansen et al.) pertains to an improved coated abrasive backing having a flexible substrate and a multiplicity of weft free, closely spaced, stretch resistant, longitudinally aligned, coplanar, continuous filament reinforcing yarns bonded to one surface of the flexible substrate before the backing is seamed into an endless belt. Each filament of the plurality of yarns would have ends which must be joined to provide the backing substrate, providing a discontinuity and probable weak area in the backing.
U.S. application Ser. No. 08/199,835 (Christianson et al.) filed 22 Feb. 1994 and assigned to the present assignee, pertains to a endless, spliced abrasive backing having reinforcing fibers.
PCT Published Patent Application No. WO 93/02837 (Luedeke et al.) published 18 Feb. 1993 and assigned to the present assignee teaches the dressing and truing of coated abrasive belts.
U.S. application Ser. No. 08/199,679 (Benedict et al.) filed 22 Feb. 1994 and assigned to the present assignee teaches a method of making an endless reinforced abrasive article comprising a sheet substrate, reinforcing fibrous material, and a binder which bonds the fibrous material to the substrate which also doubles as a make coat for adhering abrasive grain to the substrate.
Users of spliceless coated abrasive belts continue to seek stronger, more durable coated abrasive belts which are substantially free of surface and/or thickness irregularities.